1. Field
The present invention relates to a method of controlling a polarity of data voltage and a liquid crystal display using the same.
2. Related Art
A liquid crystal display of an active matrix driving type displays a moving picture using a thin film transistor (hereinafter, referred to as “TFT”) as a switching element. The liquid crystal display may be manufactured in a small size unlike a cathode ray tube (CRT), such that the liquid crystal display is applied to a television as well as a display for a portable information device, office equipment, a computer, or the like to quickly replace the CRT.
Liquid crystal cells of the liquid crystal display may display an image by changing transmissivity in accordance with a potential difference between a data voltage supplied to a pixel electrode and a common voltage supplied to a common electrode. In order to reduce an afterimage, and to prevent deterioration of the liquid crystal, the liquid crystal display is driven in inversion driving method that periodically reverses the polarity of the data voltage applied to the liquid crystal.
Generally, the liquid crystal display controls the polarity of the data to be written to the pixels of a 1 line in response to a polarity control signal POL of which polarities are inverted by 1 horizontal period unit. In the liquid crystal display, the image quality of the liquid crystal display may be deteriorated according to a correlation between the data pattern of the input image with the polarity of the data voltage. As an example, positive and negative data displayed in the pixels of the 1 line are unbalanced, either polarity becomes stronger. When the polarity of the data to be written to the pixels of the 1 line is biased to any one of the polarity, the common voltage Vcom may be shifted. Non-uniformity of the polarity may be determined based on an accumulated direct current (DC) value by counting the polarity of the high gray level data from the 1 line data. Since the reference potential of the liquid crystal cells is changed when the common voltage Vcom is shifted, a user may feel a phenomenon such as a smear, a greenish or a flicker from the image displayed on the liquid crystal display. In the case in which touch sensors are embedded in the liquid crystal display panel in an in-cell type, if the common voltage Vcom is shifted, the recognition rate of the touch sensor may be deteriorated by varying an offset value of the touch sensor signal.